The invention is directed to a lobed or profiled, finefiber filament yarn with a yarn viscosity RV of 40 to 55 and a tenacity of 30 to 45 cN/tex, particularly as a feed yarn for texturing, and to a process for the production of same.
Profiled poly(hexamethylene adipamide) yarns are known (U.S. Pat. No. 4,801,503). The known yarn has a smooth filament with a ribbon-shaped fiber cross section and a filament titer of 2.8 dtex which is suitable as a spandex substitute for the production of hosiery because of its high flexural strength. The low modulus of flexure is due chiefly to the special profiling. The known yarn is produced in two steps as a socalled polyamide LOY yarn.
By polyamide LOY is meant a filament which is wound up at spinning take-off rates of up to approximately 1800 m/min. Polyamide POY is produced by spinning take-off rates between 3700 and 5000 m/min.
A particular disadvantage of polyamide LOY for the proposed use of the present yarn consists in the low spinning rates so that economical production cannot be ensured. A further disadvantage is the pc, or subsequent processing (yarn breakage) of polyamide Loy at high speeds.
As is also known, there has been no success so far in producing finer, profiled filaments with sufficient dyeing uniformity in textile fabrics with acceptable titer uniformity (U%). The production of profiled filaments in the titer range of smooth hosiery yarns with a fineness of dtex 22 f 8, i.e. a filament titer of roughly 2.8 dtex, can easily be accomplished.
On the other hand, the production of a fine-fiber profiled feed yarn of poly(hexamethylene adipamide) (Nylon 6/6) POY involves considerable difficulties. This may be due to the fact that a round fiber cross section represents an ideal which is strayed from considerably in profile spinning. In melt or extrusion spinning, the yarn forming process becomes increasingly unstable with increasing fineness of the fiber. This is manifested chiefly in the sharp reduction in titer uniformity and in irregular dyeing results in the finished fabric. These disadvantages are more pronounced in the extrusion spinning of polyamide POY.
The yarn viscosity is measured in a known manner as relative viscosity (RV) in formic acid.
To determine the uniformity of color, a segment of stocking is knitted from a number of random spinning reels of a batch. The stocking segment is dyed in a known manner in a bath with alizarin light-blue 4GL dye manufactured by Sandoz AG, Basel, and, after drying, the different reflectance (luminosity or brightness) of segments originating from different spinning reels is measured by colorimetry. The coefficient of variation is calculated in a known manner from the reflectance.